Gullible rhymes with:
appealable, available, billable, callable, consolable, controllable, fallible, incalculable, infallible, inhalable, inviolable, irreconcilable, noncallable, recyclable, resealable, salable, saleable, syllable, unassailable, unavailable, uncontrollable, unsalable, unsaleable, valable, violable
Gullible sounds like:
gleeful, gleefully, glibly, global, globally, guilfoil, guilfoyle